There are 2 rules that when I follow, always give me a good nights sleep. If I break either one of the rules then I always have a crap sleep. Because I cherish a good quality sleep I simply refuse to break either one of these two rules.
Rule Number 1: Do not watch anything that is remotely capable of putting you on the edge of your seat after 6pm. No Action movies, dramas or anything too exciting after 6. Comedies and documentaries are fine but a few pages from a good book is ideal.
Rule Number 2: Make sure you've had enough sugar. Most of us have unknowingly developed a (refined) sugar addiction because of all the crap that's in our food. If you're someone who eats healthy and typically avoids refined sugars that's excellent. But because you're addicted your brain function is compromised when it comes to regulating your thoughts and so this affects your ability to switch off when it's bedtime. Enough fruit or any other source of natural sugar is the answer to a good nights sleep if you're a healthy person who tends to avoid refined sugars.